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Organizing Life’s Diversity
17
The Big Idea
Evolution underlies the
classification of life’s
diversity.
Main Idea #1
Biologists use a system of classification to organize information
about the diversity of living things.
Classification
Biologists use a system of
classification to organize
information about the diversity of
living things.
Classification is the grouping of
objects or organisms based on a
set of criteria.
Early Systems of
Classification
Aristotle
More than 2000 years ago, Aristotle developed the first widely accepted system of
biological classification.
Aristotle classified organisms as either
Animals were classified according to
absence of “red blood.”
Animals were further grouped according
and morphology.
Plants were classified by average size
trees, shrubs, or herbs.
animals or plants.
the presence or
to their habitats
and structure as
Aristotle’s classification system was believed to be accurate until rapid scientific
exploration caused many new species to be discovered.
Using common names for so many organisms was causing problems since names
varied from one location to the next.
Early Systems of
Classification
Linnaeus
In an attempt to organize the system, a Swedish naturalist named Carolus Linnaeus, came
up with a system that grouped organisms into hierarchical categories.
Linnaeus’s system of classification was
taxonomy.
He used the organisms’ morphology
His system consisted of seven levels
kingdom,
family, genus, and species.
the first formal system of
(form and function)
of organization:
phylum (or division), class, order,
Early Systems of
Classification
Linnaeus’s method of naming
organisms, called binomial
nomenclature, gives each species
a scientific name with two parts.
The first part is the genus name,
and the second part is the specific
epithet, or specific name, that
identifies the species.
Ursus
americanus
(AKA the “Rebel”
Black Bear)
Rules for Scientific
Names
The first letter of the genus name always is capitalized, but the rest of the
genus name and all letters of the specific epithet are lowercase.
If a scientific name is written in a printed book or magazine, it should be
italicized (e.g., Homo sapiens).
When a scientific name is written by hand, both parts of the name should
be underlined (e.g., Homo sapiens).
After the scientific name has been written completely, the genus name will
be abbreviated to the first letter in later appearances (e.g., H. sapiens).
Taxonomic Categories
The taxonomic categories used by
scientists are part of a hierarchy
system.
Each category is contained
within another, and they are arranged
from broadest to the most specific, or
largest
to
smallest.
Each named group
is called a taxa.
Main Idea #2
Classification systems have changed over time as
information has increased.
What is a species?
How are things
classified?
To classify a species, scientist construct
patterns of descent by using characters.
These characters may morphological or
biochemical.
Morphological Characters
Shared morphological characters suggest that species
are related closely and evolved from a recent common
ancestor.
Analogous characters may have similar functions but
different underlying construction , while homologous
characters may appear similar but have differing
functions.
Compare birds and
dinosaurs:
Theropods have leg, wrist,
hip, and shoulder structures
similar to birds.
Both have hollow bones.
Some theropods may have
had feathers.
Biochemical Characters
Scientists use biochemical characters, such as amino
acids and nucleotides, to help them determine evolutionary
relationships among species.
Scientists will also compare the DNA and RNA between
species to determine how similar or different they are.
The similarity between the chromosomes of the
chimpanzee, gorilla, and orangutan suggests a
common ancestor.
Molecular Clocks
Scientists use molecular clocks to compare
the DNA sequences or amino acid
sequences of genes that are shared by
different species.
The differences between the genes
indicate the presence of mutations.
The more mutations that have
accumulated, the more time that has
passed since divergence.
Phylogenic
Reconstruction
Cladistics reconstructs phylogenies
based on shared characters.
A cladogram can be used to
show the amount of shared
characters.
The greater the number of
derived characters shared by
groups, the more recently the
groups share a common
ancestor.
Main Idea #3
The most widely used biological classification system has six
kingdoms within 3 domains.
Domains & Kingdoms
Grouping Species
The broadest category in the classification used by most biologists is
the domain.
The most widely used biological classification system has six kingdoms
and three domains.
The three domains are Bacteria, Archaea, and Eukarya.
The six kingdoms are Bacteria, Arcahea, Protisits, Fungi, Plantae, and
Animalia.
Domain Bacteria
Typical Bacteria
Prokaryote
Unicellular
Most have a cell wall
Most make own food by photosynthesizing
Reproduce by conjugation and binary fission
Used to make antibiotics and flavor for some
foods
Domain Archaea
Bacteria
Extremophiles
Prokaryote
Unicellular
Have a cell wall
Make own food
Reproduce by conjugation and binary fission
Ribosomal RNA holds genetic code
Domain Eukarya
Classifies all eukaryotes.
Contains kingdoms
protista, fungi, plantae, and
animalia.
Kingdom Protista
Uni/Multicellular
Some make food via
photosynthesis
Reproduce through conjugation,
binary fission, mitosis, or meiosis.
Some have a cell wall made of
cellulose
Most diverse kingdom
Amoebas, Euglena, Diatoms,
3 Groups
Algae
Plantlike
Animallike
Funguslike
Kingdom Fungi
Uni/Multicellular
Cannot make its own food
Reproduce through fission,
fragmentation, budding, spores
(sexual/asexual)
Cell wall made of chitin or
cellulose
Can be fatal to humans
Mushrooms, Yeast, Lichen
Kingdom Plantae
Multicellular
Makes food via photosynthesis
Reproduce through vegetative
propagation, sexual spores, and
pollination
Cell wall made of cellulose
Mossess, grasses, trees, flowers
Kingdom Animalia
Multicellular
No cell wall
Does not make its own food.
Internal/External Fertilization
Vertebrates/Invertebrates
Symmetrical
Symmetry
Asymmetry
Bilateral
Radial
No Symmetry
Can be divided into 2
equal halves with
only one line
Grouped around a
central point, can be
divided many ways to
get mirror images.
Types of Sexual
Reproduction
Types of Asexual
Reproduction